1. Field of the Invention
This invention relates to a process and an apparatus for manufacturing a pressed powder body from ultrafine particles.
2. Description of Relevant Information
It has been hitherto known that where it is required for a structural material to have predetermined characteristics such as predetermined strength, hardness, toughness, durability, etc., there is manufactured, by a conventional forming process such as a melting cast process, a sintering process or the like, an integral composite product comprising any kind of metal or any kind of alloy constituting the main component of the product and any different kind of metal, alloy or compound such as a metallic oxide or the like.
For obtaining a product having predetermined characteristics, it is necessary to manufacture a lump or agglomerate product having a uniform structure comprising a mixture, for example, of two different metals or a metal and a compound such as an oxide. A product meeting this requirement cannot be obtained by conventional manufacturing processes. Namely, in the foregoing lump forming process, metallic particles and compound particles, after being mixed together, are heated to be brought into a molten condition thereof or are subjected to a high temperature-elevated sintering condition that causes extremely vigorous moving and dispersing between atoms thereof, so that the particles are mutually fused together, and thereby a predetermined dispersed condition of the particles at the time of mixing thereof is easily destroyed to result in a composite product comprising an extremely non-uniform mixed structure of different kinds of materials. Thus, it is difficult to maintain, at a final stage of the process, a predetermined structure which uniformly possesses suitable predetermined characteristics.
To cite concrete examples, for manufacturing a dispersed reinforced alloy composite product, it is necessary, for example, to disperse ultrafine particles of metallic oxide in a metallic matrix. In this case, however, a mixture thereof is heated for several minutes to a high temperature that is at least 60% higher than the melting point of the metallic material, so that it is difficult to presume the characteristics of the product after being solidified or cooled. In the case of a melting cast process, the influence on a cast product caused by segregation due to gravity while maintaining the molten condition thereof cannot be neglected. In the case of a sintering process, it is difficult to obtain a uniform mixture of components of a composite product at the time of mixing thereof before the mixture is formed into a sintered product, and additionally there is caused growing of the particles at a temperature of above about 500.degree. C. Consequently, there cannot be obtained a lump form product having a uniform composite structure.
The present invention has for an object to provide a manufacturing process which can avoid the foregoing defects of the conventional processes, and which can obtain a predetermined uniform mixing condition and produce a pressed powder body comprising a lump form product having a predetermined uniform composite structure without changing the foregoing predetermined mixing condition obtained by the mixture.
Additionally, this invention has as another object to provide a process for manufacturing a pressed powder body which has a predetermined uniform structure and is higher in density or compactness and more excellent in various characteristics than products produced by conventional processes.
The present invention has as a further object to provide a manufacturing apparatus which is made in relation to each of the foregoing processes and is suitable for carrying out the same.